High environmental temperatures during exercise can increases your heart rate above normal levels because your heart has to send blood to your skin to cool you down while continuing to supply blood to your working muscles. These two demands force your heart to beat faster. read more
Exercise increases the rate at which energy is needed from food. This increases the need for both food and oxygen in the body. This is why your pulse rate and breathing rate increase with exercise. Your pulse is just an indication of your heart rate as your arteries expand each timethe ventricles pump blood out of the heart. Your heart speeds up to pump extra food and oxygen to the muscles. read more